Thin film electroluminescent (TFEL) display panels offer several advantages over older display technologies such as cathode ray tubes (CRTs) and liquid crystal displays (LCDs). Compared with CRTs, TFELs display panels require less power, provide a larger viewing angle, and are much thinner. Compared with LCDs, TFEL display panels have a larger viewing angle, do not require auxiliary lighting, and can have a larger display area.
FIG. 1 shows a prior art TFEL display panel 10. The TFEL display has a glass panel 11, a plurality of transparent electrodes 12, a first layer of a dielectric 14, a phosphor layer 16, a second dielectric layer 18, and a plurality of metal electrodes 20 perpendicular to the transparent electrodes 12. The transparent electrodes 12 are typically indium-tin oxide (ITO) and the metal electrodes 20 are typically A1. The dielectric layers 14, 18 act as capacitors to protect the phosphor layer 16 from excessive currents. When an electrical potential, such as about 200 V, is applied between the transparent electrodes 12 and the metal electrodes 20 by a source 22, electrons tunnel from one of the interfaces between the dielectric layers 14, 18 and the phosphor layer 16 into the phosphor layer where they are rapidly accelerated. The phosphor layer 16 typically comprises ZnS doped with Mn. Electrons entering the phosphor layer 16 excites the Mn causing the Mn to emit photons. The photons pass through the first dielectric layer 14, the transparent electrodes 12, and the glass panel 10 to form a visible image. FIG. 2 illustrates a cross selectional view of the prior art TFEL display cut along the line AA 24 of FIG. 1.
Although current TFEL displays are satisfactory for some applications, more advanced applications require brighter higher contrast displays, larger displays, and sunlight viewable displays. One approach for increasing the brightness of the display is to use low resistance transparent electrodes which allows the display to be driven faster and hence increases the displays brightness. A problem with this approach is that while metal bus bar overlaps the transparent electrode to decrease electrode resistance, the overlapping structure interferes with light emitted from each pixel since pixel area is reduced, thus reducing the obtainable brightness of the display. If the electrode resistance can be reduced, the display can be driven faster resulting in brighter display.